The present invention relates to thin sheet material which can be readily torn along a predetermined tear line while retaining its integrity until the material is torn. Such structures are highly desirable for a variety of uses. For example, aluminum foil is customarily used to cover frozen foods and often portions thereof must be selectively torn for food preparation. Flexible plastic sacs or pouches containing food must be opened quickly and easily to release the contents. A particular use is for plastic lids commonly used with rigid containers, such as cups, tubs, jars, cans and the like. For example, all kinds of drinks are currently being dispensed in plastic and paper containers commonly being covered with openable lids. A problem is often encountered with spillage when the lid has been opened. For cold drinks the problem has been often reduced by providing a selectively opened straw orifice in the lid; however, this is mostly undesirable as most users prefer to drink from a substantial opening rather than through a straw.
A variety of flip open lids have been developed, as shown for example in U.S. Pat. Nos. 3,994,411, 3,977,559, 4,210,272, 4,202,459, 4,412,629, 4,090,660 and 4,285,442. However, these rely on the principle of scoring the lid along a predetermined line and hence weakening the material at the score site. This undesirable weakening could result in leakage of the contents of the container or accidental opening of the tear top with possible spillage.
Therefore, it is particularly desirable to provide a tearable structure which is tearable along a predetermined tear line without weakening the base structure. It is an object of the present invention to provide such a tearable structure made of plastic, aluminum or a laminated composite thereof and also a method for tearing a thin sheet material along a predetermined tear line.
It is an additional object of the present invention to provide a variety of such tearable structures, such as container lids, plastic pouch packages, metal foil, and to provide such structures which are not characterized by a weakened tear line as with a scored tear line, and which can be uniformly and reliably torn at a desired location.
Further objects and advantages of the present invention will appear hereinbelow.